diff --git a/Validator/Constraint/UniqueDocumentValidator.php b/Validator/Constraint/UniqueDocumentValidator.php
index 9b77a3e..fb7912e 100644
--- a/Validator/Constraint/UniqueDocumentValidator.php
+++ b/Validator/Constraint/UniqueDocumentValidator.php
@@ -117,7 +117,7 @@ private function createCriteria(Document $document, array $fields, array $caseIn
         foreach ($fields as $field) {
             $value = $document->get($field);
             if (in_array($field, $caseInsensitive)) {
-                $value = new \MongoRegex(sprintf('/^%s$/i', $value));
+                $value = new \MongoRegex(sprintf('/^%s$/i', preg_quote($value)));
             }
             $criteria[$field] = $value;
         }